1. Field of the Invention
The present invention relates to ultraviolet light absorber and hindered amine light stabilizer compounds, method therefore and coating compositions containing the same, wherein the compounds include a carbamate functionality.
2. Discussion of the Prior Art
Curable coating compositions such as thermoset coatings are widely used in the coatings art. They are often used for topcoats in the automotive and industrial coatings industry. Color-plus-clear composite coatings are particularly useful as topcoats where exceptional gloss, depth of color, distinctness of image, or special metallic effects are desired. The automotive industry has made extensive use of these coatings for automotive body panels. Color-plus-clear composite coatings, however, require an extremely high degree of clarity in the clearcoat to achieve the desired visual effect. High-gloss coatings also require a low degree of visual aberrations at the surface of the coating in order to achieve the desired visual effect such as high distinctness of image (DOI).
In the field of automotive coatings, it has become an objective to obtain a clearcoat (i.e., the outermost automotive coating) that is resistant to being etched by environmental fallout. Environmental etching is manifested by pitting, water spotting or chemical spotting of the coating or any combination of these. Etch resistance is desirable because it improves the appearance and useful life of the coating.
Etch resistance can be measured by visual examination of the coating, or by a profilometer or by subjecting a coating on a test panel to a saline solution in a temperature gradient oven test. Etch resistance is generally measured by visual examination by individuals skilled at examining finishes for the degree of etch therein. Etch resistance has become more important as the amount of acid rain, and other industrial fallout has increased. Currently, environmental etching of automotive finishes is generally greatest in the areas most greatly affected by industrial fallout.
The addition of UVAs and HALS generally improves the durability of coatings upon exposure to weathering. The incorporation into a coating composition of a UVA or HALS that is bound to a monomer, oligomer or polymer in a coating composition, stabilizes the UVA or HALS, prevents migration of the UVA or HALS into other coating layers and retains the UVA or HALS in the clearcoat, where it is needed.
Coatings containing carbamate functional resins or additives show little or no improvement in etch resistance with free additions of durability enhancing agents (i.e. HALS or UVAs that are not polymer- or oligomer-bound). It was unexpectedly found that the addition of HALS or UVAs bound to polymers- or oligomers including a carbamate functionality provide greater etch resistance of a cured coating film, than that obtainable with a carbamate functional resin alone.